Apparatus for the continuous path-controlled sharpening of saw toothings

ABSTRACT

The apparatus comprises a saw blade holder (24), a grinding slide (30) which carries a profiled grinding wheel (38) and is movable to and fro in a strokewise manner with respect to the saw blade holder (24), and a feed slide (40) by means of which a saw blade (10) in the saw blade holder (24) can be advanced in a stepwise manner. A dressing template (50) is arranged at the apparatus in a normally inoperative position and can be moved in intervals into an operative position in which the grinding wheel (38) is dressed by plunging into the dressing template (50). The feed slide (40) can be put out of operation during the dressing intervals. The stroke of the grinding slide (30) is adjustable prior to the next plunging motion into the saw blade (10) corresponding to the radius decrease of the grinding wheel (38) effected by dressing. This simplifies the dressing operation of the grinding wheel (38) and shortens the time required for each dressing operation.

In such apparatuses the grinding slide on the one hand and the feedslide on the other hand are controlled by a CNC control or a cam controlsystem in such a manner that the grinding wheel plunges along a toothface each into a tooth gap of the toothing of a saw blade while the feedslide remains stationary. As soon as the grinding wheel has reached thebottom of the tooth, a feed motion of the saw blade commences which isinitiated by a driver in the form of a finger or a latch, which issupported at the feed slide, acting on a neighbouring tooth face. Duringthe feed motion the grinding wheel generally plunges still deeper intothe bottom of the tooth, and is then gradually retracted in order tosharpen the adjacent tooth back and finally its uppermost part whichbelongs to the tooth tip, the so-called flank. For this type ofcontinuous path-controlled sharpening of saw toothings a grinding wheelis required which at its periphery comprises a profile which is adaptedin a certain manner to the toothing profile.

Due to wear, the grinding wheel periphery gradually assumes a deviatingprofile; it is therefore necessary to dress the grinding wheel from timeto time. For this purpose, the use of dressing diamonds is known whichact on the grinding wheel in a spot-type manner and which can be movedunder continuous path control in an own coordinate system, which isindependent of the grinding device. Diamond dressing rolls are alsoknown with a profile which complements the intended peripheral profileof the grinding wheel and which are also supported in an own device tobe adjustable in at least two coordinates so that they can be broughtinto engagement with the grinding wheel which is only rotating while thegrinding slide is stationary.

The invention is based on the object to simplify the dressing ofgrinding wheels in an apparatus for the continuous path-controlledsharpening of saw toothings and to shorten the required time for eachdressing operation.

The dressing template according to the invention which preferablyconsists, at least partially, of polycrystalline diamond requires littlespace and can therefore be located at the apparatus for the continuouspath-controlled sharpening of saw toothings in the immediate vicinity ofthe saw blade in a space-saving manner in an inoperative position wherethe template does not interfere with the sharpening of saw toothings. Inthe sharpening intervals the template has therefore to cover only asmall travel from its inoperative position into a preferably stationary,i.e. not variable, operative position in order to provide the conditionsfor the grinding wheel to now plunge into the template instead of intothe saw toothing, by means of which it will be dressed in a singleworking stroke of the grinding slide. The dressing operation by means ofthe template differs from the normal operation during sharpening of sawtoothings merely in that the feed slide is put out of action, i.e.either stopped entirely or rendered inactive in another manner, duringthe dressing intervals and that the stroke of the grinding slide isshifted or shortened.

An embodiment of the invention will be described in the following withreference to schematic drawings with further details. In the drawings:

FIG. 1 shows the front view of an apparatus according to the invention;and

FIG. 2 shows the side view in the direction of the arrow II in FIG. 1.

In the drawings, a band saw blade is illustrated as an example of a sawblade 10 the toothing of which is to be sharpened; in the presentcontext, however, the term saw blade covers a mill saw blade or acircular saw blade as well. In each case, a saw blade 10 with teeth 12is involved, which are machined in a continuous path-controlledsharpening operation at their tooth faces 14 and additionally at theirtooth bottoms 16 and tooth backs 18.

The apparatus for the sharpening of the saw blade 10 has a machine frame20 with a saw blade guide 22 which in the illustrated example is formedby a horizontal rail and adjustable in height corresponding to the widthof the saw blade 10. Above the saw blade guide 22 a saw blade holder 24is arranged which in the illustrated example has a stationary jaw 26 andan adjustable jaw 28. The adjustable jaw 28 is biased in the usualmanner in the direction of the stationary jaw 26 so that the saw blade10 is held between the jaws in a vibration-free manner without beingimpeded in a feed motion.

At the machine frame 20 a grinding slide 30 can be moved upwards anddownwards under an adjustable angle relative to the saw blade guide 22in the direction of the double arrow A by means of a stroke drive 32. Atthe grinding slide 30 a grinding spindle 34 is supported which can bedriven rotatably by means of a motor 36 and which carries a grindingwheel 38.

Furthermore, at the machine frame 20 a feed slide 40 is movable to andfro in parallel to the saw blade guide 22 in the sense of the doublearrow B by means of a feed drive 42. The feed slide 40 carries a crossslide 44 which is movable normally to the plane of the saw blade 10, atwhich cross slide a feed arm 46 is arranged in parallel to the plane ofthe saw blade 10.

The feed arm 46 comprises at its front end a feed finger 48 whichextends normally to the plane of the saw blade 10 and is adjustable insuch a manner that the feed finger can be brought into contact with thetooth face 14 of a tooth 12 with each working stroke in order to pushthe saw blade 10 depending on the setting of the feed drive 42 by one orseveral tooth spacings in a forward direction. The cross slide 44 isretractable from its illustrated operative position into an inoperativeposition in which the feed finger 48 does not reach the plane of the sawblade 10; in this inoperative position the feed slide 42 is thereforenot operative in the sense of its normal function.

For the purpose of dressing of the grinding wheel 38 a template 50 isprovided which is either a plate which consists entirely ofpolycrystalline diamond (PCD) or a compound plate where one or severalPCD plates are soldered or glued onto a hard metal plate which in turncan be reinforced by a steel plate. The dressing template 50 isreplaceably attached at a template holder 52 which in the illustratedexample is formed by a two-arm lever and is supported at a bracket 54 soas to be pivotable about an axis C extending parallel to the plane ofthe saw blade 10 and to the feed direction (arrow B). The dressingtemplate 50 is shown in its operative position; in this case it lies inclose vicinity to the plane of the saw blade 10 within a plane whichcontains the axis of rotation D of the grinding wheel 38. From thisoperative position which is defined by an adjustable stop which is notshown, the template holder 52 together with the dressing template 50 canbe pivoted by means of a piston/cylinder unit 56 about the axis C awayfrom the saw blade 10 into an inoperative position in which it can becontacted by neither the saw blade 10 nor the grinding wheel 38. Thepiston/cylinder unit 56 is supported at the bracket 54, and its pistonrod 58 is connected in an articulated manner with the template holder52.

For the purpose of dressing of the grinding wheel 38 the feed drive 42is appropriately shut down, but at least the cross slide 44 is movedinto its inoperative position so that the feed finger 48 cannot engagethe toothing of the saw blade 10. The dressing template 50 is thenpivoted into its operative position. All of this can be effected duringa normal return stroke of the grinding slide 30 after a grinding stroke.The next downward stroke of the grinding slide 30 is modified eitherCNC-controlled or by changing a cam drive which normally drives thegrinding slide in such a manner that the grinding wheel 38 does notplunge into the saw blade but only into the dressing template 50 whoseoperative position is slightly higher than the toothing of the saw blade10. The lower end point of this downward stroke determines the amount bywhich the grinding wheel 38 will be dressed. With the next upward strokethe stroke drive 32 is reversed again to normal operation, however, withthe amount by which the radius of the grinding wheel 38 was reduced inthe dressing operation being compensated by shifting of the lower end ofthe travel distance of the grinding slide 30. At the same time, thedressing template 50 is pivoted back into its inoperative position. Thenext cycle can already be a normal sharpening cycle during whichcoordinated motions of the grinding slide 30 and the feed slide 40 arecarried out and result in correspondingly coordinated motions of thegrinding wheel 38 and the saw blade 10 so that the sharpening operationof the saw blade 10 can be continued.

We claim:
 1. An apparatus for the continuous path-controlled sharpeningof saw toothings, comprisinga saw blade holder (24), grinding slide (30)which carries a profiled grinding wheel (38) and is movable to and froin a strokewise manner with respect to the saw blade holder (24), and afeed slide (40) by means of which a saw blade (10) in the saw bladeholder (24) can be advanced in a stepwise manner, characterized in that,a dressing template (50) is arranged at the apparatus in a normallyinoperative position and is adapted to be moved in intervals into anoperative position in which the grinding wheel (38) is dressed byplunging into the dressing template (50), the feed slide (40) is adaptedto be put out of operation during the dressing intervals, the stroke ofthe grinding slide (30) is adjustable prior to the next plunging motioninto the saw blade (10) corresponding to the radius decrease of thegrinding wheel (38) effected by dressing, which is further characterizedin that the dressing template (50) in its operative position is arrangedadjacent to the saw blade holder (24), and further characterized in thatthe dressing template (50) is adapted to be pivoted about a pivot axis(C) which extends parallel to the saw blade (10) from its inoperativeposition into its operative position.
 2. The apparatus according toclaim 1, characterized in that the dressing template (50) is replaceablyattached at a template holder (52).
 3. The apparatus according to claim2, characterized in that the template holder (52) is supported at thesaw blade holder (24).
 4. The apparatus according to claim 1,characterized in that the dressing template (50) is a plate which atleast partially consists of polycrystalline diamond.
 5. An apparatus forthe continuous path-controlled sharpening of saw toothings, comprisingasaw blade holder (24), a grinding slide (30) which carries a profiledgrinding wheel (38) and is movable to and fro in a strokewise mannerwith respect to the saw blade holder (24), and a feed slide (40) bymeans of which a saw blade (10) in the saw blade holder (24) can beadvanced in a stepwise manner, characterized in that, a dressingtemplate (50) is arranged at the apparatus in a normally inoperativeposition and is adapted to be moved in intervals into a stationaryoperative position in which the grinding wheel (38) is dressed byplunging into the dressing template (50), whereby the grinding wheel(38) will be dressed in a single work stroke of the grinding slide (30),the feed slide (40) is adapted to be put out of operation during thedressing intervals, and the stroke of the grinding slide (30) isadjustable prior to the next plunging motion corresponding to the radiusdecrease of the grinding wheel (38) effected by dressing.